In the related art, as a gasification unit, a carbonaceous fuel gasification unit (gasification unit) is known, which supplies carbonaceous feedstock such as coal into a gasifier and partially combusts the carbonaceous feedstock to gasify the carbonaceous feedstock so as to generate a combustible gas. A furnace monitoring device for monitoring a situation in a furnace is provided in the gasification unit (for example, PTL 1).
PTL 1 discloses the furnace monitoring device including a cooling fluid passage which passes through an equipment housing portion housing a camera and a cleaning fluid passage which cleans a monitoring window which separates the inside of the furnace from the equipment housing portion. In the furnace monitoring device disclosed in PTL 1, air flows through the cooling fluid passage to cool an imaging device, and cleaning air or washing water blows from an ejection hole disposed at a tip of the cleaning fluid passage toward the monitoring window to clean the monitoring window.